The U.S. Food and Drug Administration on Thursday ruled that trans fats aren’t safe in food, a major shift that follows a divisive New York City ban on trans fats that was spearheaded by Mayor Michael Bloomberg and approved in 2006. The FDA will give food companies 60 days to comment on its proposed measures to take steps towards eliminating trans fats from the American food supply and then make a final ruling.

“New York City deserves a great deal of credit for this,” said Samantha Levine, a spokeswoman for Mr. Bloomberg, in an interview.

But the F.D.A. isn’t patting Mr. Bloomberg’s back.

“I don’t think you can say that,” said Shelly Burgess, a spokeswoman for the FDA , when she heard Ms. Levine’s comment.

Asked if the FDA viewed New York City’s trans fats ban as an influence in the federal policy change — which could result in a ban on the substance — Ms. Burgess said: “I would need to check further into that. I mean, the FDA has been looking at trans fat for years … we base our decisions on science.” Ms. Burgess pointed out that the FDA by 2006 required manufacturers to include trans fats content on nutritional labels.

Mr. Bloomberg’s trans fats ban was not fully enforced until July 2008.

The mayor also released a statement that reads in part: “Our prohibition on trans fats was one of many bold public health measures that faced fierce initial criticism, only to gain widespread acceptance and support.” And a Washington Post blog post today credited Mr. Bloomberg with influencing Thursday’s ruling.

The city’s ban was contested at the time by groups like the National Restaurant Association. That organization today released a statement on the federal policy change that said “we plan to discuss the impact of this” — rhetoric that is toned down since the organization’s qualms with New York City’s ban.

Ms. Levine said Mr. Bloomberg has “definitely had a big impact” on national health policies, citing the proliferation of smoke-free restaurants and the posting of food calorie counts.

She said she hopes Mr. Bloomberg’s measure to ban sugary beverages of a certain size is the next policy to go national – though it was locally struck down by the State Supreme Court. “The proposal … has already started a national conversation around obesity and sugary drinks,” Ms. Levine said. “That’s something we would like to become law in New York City and nationally.”